This isn't in response to your question, but your incorrect use of $|++.

$|++; turns on autoflushing for the currently selected file handle, not for your pipe. Both of the following snippets turn on autoflushing:

### Forces a flush after every write to this pipe.
my $old_fh = select(PIPE);
$|=1;
select($old_fh);
[download]

use IO::Handle qw( );

### Forces a flush after every write to this pipe.
PIPE->autoflush(1);
[download]

But the thing is, INOTIFY is a reader pipe. You never write to it, so it's useless to turn on autoflushing for it.